Artificial suede-type leather and process for producing the same

ABSTRACT

This invention relates to a suede-like artificial leather using ultra-fine polyester fibers and a polyurethane, and provides a suede-like artificial leather free from the occurrence of specking and having graceful surface appearance and high light fastness. The suede-like artificial leather comprising a fiber-entangled substrate mainly containing ultra-fine polyester fibers with a fiber fineness of 0.7 dtex or less and a polyurethane, and is dyed, and is wherein said polyurethane contains at least one each of yellow pigments, red pigments and blue pigments, and that said artificial leather satisfies all of the following properties (1) through (3) as measured by the methods described in the specification; (1) The infrared reflectance at 850 nm is 60% or more; (2) The surface temperature during light irradiation is 105° C or lower; (3) The light fastness is class 3 or better. Especially since the suede-like artificial leather of this invention has high light fastness, it can be most suitably used for car seats.

TECHNICAL FIELD

The present invention relates to a suede-like artificial leather havingexcellent light fastness, brilliant coloration and good surfaceappearance, and also to a method for producing said artificial leather.

BACKGROUND ART

Suede-like artificial leathers with a structure in which afiber-entangled substrate composed of ultra-fine polyester fibers isimpregnated with a polyurethane are used not only in high qualityclothing field, but also in various other fields including the interiormaterials of automobiles and furniture use, since it is excellent inhigh quality appearance, surface touch, coloration, etc.

The requirements for these artificial leathers in view of sensibilityand functions are more and more sophisticated in recent years.

For example, as for the properties required in view of sensibility,further improvement of softness as leather stuff and further improvementof surface appearance are required, and as for the properties requiredin view of functions, further improvement of light fastness is required.

Among them, the improvement of light fastness is one of the mostimportant properties especially in the use for the interior materials ofautomobiles.

That is, in the use for the interior materials such as seats of carsrunning outside, it usually occurs that the interior materials areexposed to light such as sunlight for long periods of time duringdriving, parking, or the like. If this is repeated for years, thereoccurs a phenomenon that the color beautiful in the beginning isdegraded gradually.

The phenomenon of color degradation (discoloration and fading) andcrocking in contrast to the very deep colored beautiful state rich inhigh quality impression of a new car in the beginning makes one feel alarge difference. Furthermore, a car owner who feels affection for thecar wishes to use the car for 5 years or 10 years or even for a longerperiod of time. So, any improvement is required to be made forpreventing the color degradation and crocking.

That is, it is desired, as improvement of color fastness, that theinitial beautiful color of a brand-new artificial leather is maintainedeven if it is used in severe conditions for a long period of time.

Meanwhile, usually a suede-like artificial leather composed ofultra-fine polyester fibers and a polyurethane as described above isdyed and colored under the condition of dyeing the polyester.

However, in general, a disperse dye used for dyeing a polyester has anessential problem that since the dye holding power of a dyedpolyurethane is weak, the dye is likely to bleed out for immediatelylowering the color fastness of the artificial leather product.

To improve this problem, reduction cleaning is carried out for, forexample, decomposing or decoloring the dye in the polyurethane. However,on the other hand, the treatment of reduction cleaning involves anotherproblem that the polyurethane becomes while conspicuously.

This means the following. In general, if such dyed artificial leatherproducts are classified in terms of color densities of the products,they can be classified into three classes; light colored products,medium deep colored products and deep colored products. If the reductioncleaning treatment is carried out, especially for medium deep colored ordeep colored artificial leathers, the polyurethane becomes whitish, toremarkably lose the color depth, thus remarkably degrading the surfaceappearance. So, no graceful artificial leather giving a high qualityimpression can be obtained.

Therefore, hitherto, for sufficiently withstanding the reductioncleaning and for making the whiteness of the polyurethane inconspicuous,a method of adding carbon black particles to a polyurethane is used(JP49-22682B).

As another method, furthermore, to make the whiteness of thepolyurethane inconspicuous, a method of adding a black pigment capableof reflecting near infrared radiation such as a perylene-based blackpigment or azomethine-azo-based black pigment, to a polyurethane isproposed (JP5-321159A).

However, in the former method (JP49-22682B), in the case where carbonblack particles are added to a polyurethane, if light is irradiated, thecarbon black absorbs infrared radiation to accumulate heat. So, thesurface temperature of the artificial leather per se rises to have ahigh temperature, for promoting the decomposition of the dye in theultra-fine fibers. In this regard, the method involves another problemthat light fastness is remarkably lowered.

Furthermore, in the latter method (JP5-321159A), in the case where apolyurethane containing a perylene-based black pigment or anazomethine-azo-based black pigment capable of reflecting near infraredradiation is used, the inventors variously examined and found that theseblack pigments have a problem that the degree of blackness (pitchblackness) is very low, even though a high temperature as caused by saidcarbon black does not occur. Therefore, even if the pigmentconcentration is raised, there arise another problem that deep blackcannot be obtained, and in addition, a further other serious problemthat the reduction cleaning performed after dyeing causes decolorationor discoloration, to virtually deprive the polyurethane of its color inthe final product observed or to discolor in such a manner thatdifferent color zones are formed. As a result, the color depth is lost,and the surface appearance is remarkably degraded. So, no gracefulartificial leather giving a high quality impression can be obtained.

As described above, the conventional artificial leathers with astructure in which a fiber-entangled substrate composed of ultra-finepolyester fibers is impregnated with a polyurethane do not include anyartificial leather having excellent light fastness, brilliant colorationand good surface appearance. Moreover, such an artificial leather is notknown either.

DISCLOSURE OF THE INVENTION

In view of the above-mentioned matters, a first object of this inventionis to provide a suede-like artificial leather using ultra-fine polyesterfibers, which has all of excellent light fastness, brilliant colorationand good surface appearance.

Furthermore, a second object of this invention is to provide a methodfor producing a suede-like artificial leather using ultra-fine polyesterfibers, which have the above-mentioned features.

The suede-like artificial leather of this invention for achieving saidfirst object has the following constitution.

That is, a suede-like artificial leather, which comprising afiber-entangled substrate mainly containing ultra-fine polyester fiberswith a fiber fineness of 0.7 dtex or less and a polyurethane and isdyed, wherein said polyurethane contains at least one each of yellowpigments, red pigments and blue pigments, and said artificial leathersatisfies all of the following properties (1) through (3) as measured bythe methods described in the specification;

(1) The infrared reflectance at 850 nm is 60% or more;

(2) The surface temperature during light irradiation is 105° C. orlower;

(3) The light fastness is class 3 or better.

Furthermore, the method for producing a suede-like artificial leather ofthis invention for achieving said second object has the followingconstitution.

That is, a method for producing a suede-like artificial leatherexcellent in light fastness, in which a fiber-entangled substrate mainlycontaining ultra-fine polyester fibers with a fiber fineness of 0.7 dtexor less is impregnated with a polyurethane, wherein the polyurethanesolution used contains at least one each of yellow pigments, redpigments and blue pigments in such a manner that the coagulated film ofthe polyurethane solution satisfies all the following properties (4)through (6) when it is evaluated according to the methods described inthe specification;

(4) The infrared reflectance at 850 nm is 60% or more;

(5) The discoloration ratio after reduction cleaning is 20% or less;

(6) The chroma is 10 or less.

This invention enables the production of a suede-like artificial leatherhaving graceful surface appearance with a deep hue free from speckingand high light fastness, which has been a problem remaining unsolved inthe suede-like artificial leathers using ultra-fine polyester fibers.

The suede-like artificial leather of this invention thus obtained can beused suitably not only for applications as materials such as theinterior materials of automobiles, furniture use, bags, shoes, glovesand the like but also for clothing use.

THE BEST MODES FOR CARRYING OUT THE INVENTION

The suede-like artificial leather of this invention and the productionmethod thereof are described below.

The suede-like artificial leather of this invention comprising afiber-entangled substrate mainly containing ultra-fine polyester fiberswith an average fineness of 0.7 dtex or less and a polyurethane, and isformed in such a manner that the fiber-entangled substrate isimpregnated with the polyurethane.

As said ultra-fine polyester fibers, for example, polyethyleneterephthalate or any of its copolymers, polybutylene terephthalate orany of its copolymers, or polypropylene terephthalate or any of itscopolymers can be preferably used.

The ultra-fine fibers used in this invention can be obtained, forexample, by a direct spinning method, or splitting a composite fiberconvertible into a bundle of ultra-fine fibers and consisting of pluralcomponents, or dissolving and removing at least one component from acomposite fiber convertible into a bundle of ultra-fine fibers andconsisting of plural components. The impregnation of the polyurethaneper se can be carried out either before or after said splitting or saiddissolution and removal of one component.

The single fiber fineness of the ultra-fine fibers used in thisinvention is 0.7 dtex or less. However, for making the surface smoothand soft hand, 0.5 dtex or less is preferred. Furthermore, in view ofdenseness and coloration, a range from 0.01 dtex to 0.3 dtex ispreferred.

In the case where the ultra-fine fibers are produced by removing atleast one component from a composite fiber convertible into a bundle ofultra-fine fibers, the combination is only required to be such that thepolymer component to be removed can be chemically or physically removedwithout substantially damaging the ultra-fine fibers. The polymer is notespecially limited to a specific polymer, but it is preferred that thepolymer is different from the polymer of the ultra-fine fibers in thesolubility in a solvent or in decomposability. Preferred examplesinclude polyolefins, polystyrene and its copolymers, polyvinyl alcohol,polyamides, alkali-soluble copolyesters, etc.

As the form of the fibers, for example, not only an ordinary circularsection, but also a hollow section or other shaped section such astriangular section or Y-type fan-shaped section, or sheath-core typeconjugate structure fibers can be used. Forms selected from them can becombined, considering the section formability as ultra-fine fibers,spinnability, drawability, etc.

In this invention, to form the fiber-entangled substrate, a long-fiberweb is formed as in the spun-bond method, or a web is formed from shortfibers by a conventional method such as using a card cross-lapper or arandom webber. Then, needle punching or water-jet punching or acombination of them can be used for forming the fiber-entangled sheet.

To let the fiber-entangled sheet have a higher strength, it is preferredthat the fiber-entangled substrate has a structure in which a nonwovenfabric containing the ultra-fine fibers and a woven fabric or a knittedfabric are integrated. The structure can be obtained by entangling andintegrating the fibers in said web with the woven fabric or knittedfabric. In the case where a composite fiber convertible into a bundle ofultra-fine fibers is used, it is subsequently made into ultra-finefibers using a solvent, heat treatment or mechanical treatment.

In this case, a method in which a woven fabric is laminated on both thesides of or either side of a web, the laminate being treated to achieveentanglement, or a method in which several sheets of saidfiber-entangled substrate are overlaid and re-treated to achieveentanglement, the laminate being later sliced in the directionperpendicular to the thickness direction, for obtaining two sheetsrespectively with a thickness corresponding to one half of the thicknessof the laminate, can be used as found suitable for the intended purpose.

Then, in this invention, the fiber-entangled substrate containing theseultra-fine fibers is given a polyurethane. The polyurethane resin isdescribed below in detail.

As the polyurethane used in this invention, basically any polyurethanecan be used. However, in view of processability, product quality and thelike, it is preferred to use any one or two or more in combination ofpolycarbonate diols, polyester diols and polyether diols respectivelyhaving an average molecular weight of 500 to 3000 as the soft segment.

Especially in view of durability, it is preferred to use a polyurethaneelastomer formed using a compound containing 30 wt % or more, based onthe weight of all the polymer diols, of a polycarbonate diol. If therate of the polycarbonate diol in the polymer diols is less than 30 wt%, the durability may be insufficient in some cases, and this is notpreferred for some applications. In the polycarbonate diol in this case,diol structures are connected through carbonate bonds for forming apolymeric chain having a hydroxyl group each at its both ends. The diolstructure is decided by the glycol used as a raw material, and theglycol is not especially limited. It can be, for example,1,6-hexanediol, 1,5-pentanediol, neopentyl glycol,3-methyl-1,5-pentanediol, or any of their mixtures, etc.

Then, any of these polyurethanes is dissolved or dispersed into asolvent, to produce the polyurethane solution to be impregnated into thefiber-entangled substrate. The polyurethane solution can be provided,for example, as a solution of an organic solvent or as an emulsion.

In this invention, at least one each of the yellow pigments, redpigments and blue pigments with the following properties are added tothe polyurethane. For a solvent solution, DMF (dimethylformamide) or thelike is added, and for an emulsion, water is added as a solvent. Thesolution is then stirred and mixed to prepare the polyurethane solution.

In this case, as required, additives such as an antioxidant, ultravioletlight absorber, photostabilizer, antistatic agent, flame retarder,softening agent, coagulation regulator and colorant can also be added.

It is preferred that the pigments to be added to the polyurethane arenot decomposed or decolored during reduction cleaning, and can reflectthe infrared radiation for decreasing the heat accumulation during lightirradiation and for improving light fastness.

Particularly, it is preferred to select the pigments suitable for theintended purpose from among the numerous yellow pigments, red pigmentsand blue pigments respectively capable of reflecting infrared radiation.

In this invention, being yellow, being red and being blue means thatthey satisfy the following definitions.

That is, this means that each polyurethane film produced using thepolyurethane concerned and the pigment of each hue (yellow, red or blue)indicates the following numerical range. The method for producing thepolyurethane resin is the same as in the method for measuring thediscoloration ratio after reduction cleaning of pigments describedbelow.

As the measuring instrument, Minolta Spectrophotometer CM-3700d or afunctionally equivalent instrument is used. As the light source, ahalogen lamp is used, and D65 light source is used as the measuringlight source. The angle of visibility is 10 degrees, and magnesium oxideis used as the white plate for reference. The measuring diameter is 25.4mm, and SCE is used for treatment of regularly reflected light. Underthese conditions, the h* (hue angle) and C* (chroma) in the L*C*h* colorsystem specified by CIE (Commission Internationale de l'Eclairage) areobtained.

And in this invention, being yellow refers to a state in which the valueof h* is 45 to less than 135 while the value of C* is 10 or more, andbeing blue refers to a state in which the value of h* is 155 to lessthan 310 while the value of C* is 10 or more. Being red refers to astate in which the value of h* is 0 to less than 45 or 315 to less than360 while the value of C* is 10 or more.

The selection of the pigments and the mixing ratio of the pigments aremade or decided, as described below in detail, to ensure that thecoagulated film of the polyurethane solution containing the respectivepigments satisfies all the three properties of being 20% or less in thediscoloration ratio after reduction cleaning, 60% or more in theinfrared reflectance at 850 nm, and 10 or less in chroma, when testedrespectively by the test methods described later.

The suede-like artificial leather of this invention reflects, on itssurface, infrared radiation, for being prevented from rising intemperature due to the heat accumulated during light irradiation, hencebeing prevented from being lowered in light fastness, and can preventthe pigments from being discolored by reduction cleaning, being able tosustain a graceful color tone.

The suede-like artificial leather of this invention is 60% or more inthe infrared reflectance of the artificial leather surface at 850 nmwhen measured by the method described later. If the value is less than60%, the effect of preventing the heat accumulation during lightirradiation is so small as to raise the surface temperature, and theintended effect of this invention cannot be obtained.

Furthermore, the artificial leather of this invention is 105° C. or lessin the surface temperature during light irradiation. If the surfacetemperature during light irradiation is higher than 105° C., theartificial leather cannot have high light fastness, and generally thelight fastness cannot be class 3 or better. So, the intended effect ofthis invention cannot be obtained.

If the suede-like artificial leather of this invention is morepreferably constituted, the surface temperature during light irradiationis 100° C. or lower. If it is further more preferably constituted, thetemperature is 95° C. or lower, and if most preferably constituted, thetemperature is 90° C. or lower. So, it can have more excellent highlight fastness.

The artificial leather of this invention comprising a polyurethane withsuch a discoloration ratio after reduction cleaning, and having saidinfrared radiation reflection capability and said property of surfacetemperature during light irradiation can be produced by using thepigments to be added to the polyurethane, under a specific recipesatisfying said specific properties.

Particularly, for example, the selection of pigments, the combination ofthe pigments and the added concentrations of the pigments can be adaptedto satisfy the above-mentioned respective properties of (1) through (6).

As suitable pigments having the above-mentioned property values,enumerated are compounds of diketopyrrolopyrrole type, anthraquinonetype, perylene type, perynone type, quinacridone type, azo type, polyazotype, condensed azo type, imidazolone type, phthalocyanine type,isoindoline type, indigo type, thioindigo type, azomethine type,azomethine-azo type, dioxazine type, indanthrone type, flavanthronetype, pyranthrone type, etc., though not necessarily limited to them.

However, according to various findings of the inventors, among thoseenumerated above, diketopyrrolopyrrole-based pigments are preferred asred pigments, and phthalocyanine-based pigments are preferred as bluepigments. Furthermore, as yellow pigments, azo-based pigments can berespectively especially suitably used.

The property values of (4) through (6) of the polyurethane solutioncontaining said pigments refer to the values of the polyurethane as awhole containing all pigments obtained by mixing all the pigments usedfor the polyurethane. Even if any pigment used alone does not satisfythe above property values, it is only required that the values obtainedfrom the pigments mixed together are in the respective ranges. Using thepigments as a mixture is meaningful.

If the pigments are used as a mixture as described above, an artificialleather deeper in hue and more excellent in surface appearance than acase of using only any one of the pigments can be produced.

When the pigments are mixed, the mixing ratio is such that the chroma ofthe coagulated film of the polyurethane solution to be impregnatedbecomes 10 or less. In this case, the chroma of the coagulated film ofthe polyurethane solution being 10 or less means that the polyurethanehaving said pigments mixed has a hue closer to an achromatic color suchas black or gray. That is, the chroma of the coagulated film of thepolyurethane solution being 10 or less means being more blackish.

If at least one each of yellow pigments, red pigments and blue pigmentsare mixed to achieve such a chroma, the polyurethane presents a calm hueand deepens the hue of the artificial leather, providing appearancegiving a high quality impression.

When at least one each of yellow pigments, red pigments and bluepigments are mixed in this invention, according to various findings ofthe inventors, it is desirable to mix at a ratio of yellow pigment:redpigment:blue pigment=1 to 3:1 to 3:1 to 3 (by weight), though it isdifficult to generally specify.

That is, it is only required that the amounts of the respective pigmentsare virtually equal, and even if the amount of one pigment is large, itis desirable that the amount is about 2 to 3 times the amount of anotherpigment. The mixing work per se can be carried out by a pigmentmanufacturer or an artificial leather manufacturer.

It is preferred that the added amount in total of the pigments is suchthat the total solid weight of the pigments is from 0.03 to 30 wt %based on the solid weight of the polyurethane. A more preferred range isfrom 0.05 to 15 wt %. Less than 0.03 wt % is not preferred, since theeffect of coloring the polyurethane is small. Furthermore, more than 30wt % may not be preferred since the physical properties of the productmay be affected.

In this invention, the polyurethane solution having predeterminedpigments mixed as described above is impregnated into thefiber-entangled substrate, and is solidified. The solidification methodin this case can be either a wet method or a dry method. However, in thecase where soft hand is desired, a wet method is preferred.

Furthermore, as for the applied amount, it is preferred that the solidweight of the polyurethane contained is 10 to 60 wt % based on theweight of the polyester fibers. Less than 10 wt % is not preferred,since the strength of the obtained artificial leather may be weak, andmore than 60 wt % is not preferred either, since the hand may becomehard.

Moreover, this sheet is compressed to substantially remove the solvent,and dried.

Then, the sheet is, as required, split into halves in the thicknessdirection (sliced to have a thickness of ½ each), and they are raisedrespectively at lease on one side, to obtain napped sheets having thepolyurethane colored with pigments.

Furthermore, it is necessary that the suede-like artificial leather isdyed. That is, only when the artificial leather uses such a polyurethaneand is dyed, it has graceful surface appearance giving a high qualityimpression.

As the dyeing machine used for dyeing, any of usually used conventionalmachines can be used, and a jet dyeing machine can be especiallypreferably used. As the dye used, a usually used dye with excellentlight fastness selected, for example, from disperse dyes and vat dyes isdesirable, and a dye capable of reflecting infrared radiation is morepreferred.

Thus, the intended artificial leather of this invention can be obtained.

The following measuring methods 1 through 6 used in this invention aredescribed below.

1. Method for measuring the discoloration ratio after reduction cleaningof the pigments in a polyurethane film containing the pigments

2. Method for measuring the infrared reflectance of a polyurethane filmcontaining pigments

3. Method for measuring the chroma of a polyurethane film containingpigments

4. Method for measuring the infrared reflectance of an artificialleather

5. Method for measuring the light fastness of an artificial leather

6. Method for measuring the surface temperature of an artificial leatherduring light irradiation

-   1. Method for measuring the discoloration ratio after reduction    cleaning of the pigments in a polyurethane film containing the    pigments

The discoloration ratio after reduction cleaning of pigments in thisinvention refers to the degree in the change of L*-value before andafter the reduction cleaning of the film formed using the polyurethanesolution to be impregnated into a fiber-entangled structure when theartificial leather of this invention is produced. It is measured asdescribed below.

At first, a polyurethane solution (mixed solution consisting of apolyurethane, pigments, solvent, etc.) to be impregnated is prepared.This solution is adjusted to ensure that the solid content of thepolyurethane resin becomes 20% based on the weight of the entiresolution. If the solution concentration is low, the solution can beevaporated using an evaporator, or a solution that allows a polyurethanesolid content of 20% to be achieved without changing the ratio of thepigment to the polyurethane can be prepared separately.

The solution prepared like this is used to form a film for measurement.For forming a film, in the case where a polyurethane dissolved in anorganic solvent is used as the polyurethane to be impregnated, thecoagulated film is produced by the following method. The preparedpolyurethane solution is cast onto a glass sheet of 40 cm square withthe clearance adjusted to a thickness of about 300 μm using a coatingknife. The coated glass sheet is immediately is immersed in about 10liters of water having a temperature of 20° C. prepared beforehand in avessel, in such a manner that the glass sheet is kept horizontal in thewater with its coating surface kept upward and perfectly submerged inwater. The water temperature is kept in a range of 20° C.±3° C., and onehour later, the glass sheet is taken out. Then, the polyurethane film isseparated from the glass sheet and dried at 80° C. for 1 hour, to obtaina coagulated film for measurement.

Furthermore, in the case where a polyurethane emulsion is used as thepolyurethane to be impregnated, the film is formed according to thefollowing method. At first, a horizontal aluminum sheet of 40 cm squareprovided with a frame for preventing the liquid from spilling from itssides is prepared, and the said polyurethane solution is poured to aliquid height of 1 mm. Then, it is dried at 130° C. for 20 minutes,while it is kept horizontal, and the film is separated from the glasssheet.

Subsequently either of the films obtained is cut into 10 cm squares thatare treated for reduction cleaning under the following conditions.

-   A. Conditions of reduction cleaning

(1) Treating agent for reduction cleaning:

-   -   Caustic soda (solid): 3 grams    -   Hydrosulfite: 6 grams    -   GURANUP US20 (produced by Sanyo Chemical Industries, Ltd.): 1.5        grams    -   Water: 300 grams

(2) Treatment temperature and period for reduction cleaning

The treating solution is heated from about 30° C. to 80° C. at such aspeed as to reach 80° C. in 30 minutes, and used for treating at 80° C.for 30 minutes, then being cooled to 40° C., taking 30 minutes.

(3) Treating device for reduction cleaning: UR-MFNI-COLOR (produced byTexam Co., Ltd.)

After completion of reduction cleaning treatment, running water is usedto wash the film so that the treating solution can be substantiallyperfectly removed, and the washing is followed by drying at atemperature of 40° C. or lower.

The L*-values of the polyurethane film before and after the reductioncleaning treatment are measured, and with the value before treatment asL*₁ and the value after treatment as L*₂, the value A obtained from thefollowing formula is called the discoloration ratio after reductioncleaning in this invention.A=(L*₂−L*₁)/L*₁×100

-   B. Measurement of L*-value

As the measuring instrument, Minolta Spectrophotometer CM-3700d(produced by Minolta Co., Ltd.) is used. If the measuring instrumentcannot be used, a functionally equivalent instrument is used. As thelight source, a halogen lamp is used, and D54 light source is used asthe measuring light source. The angle of visibility is 10 degrees, andmagnesium oxide is used as the white plate for reference. The measuringdiameter is 25.4 mm, and SCE is used for treatment of regularlyreflected light. Under these conditions, the L*-value specified by CIE(Commission Internationale de l'Eclairage) is measured. For measurement,four overlaid films are used.

-   2. Method for measuring the infrared reflectance of a polyurethane    film containing pigments

The infrared reflectance of a polyurethane film containing pigments inthis invention refers to the infrared reflectance of the coagulated filmprepared using the polyurethane solution to be impregnated into afiber-entangled substrate when the artificial leather of this inventionis produced. It is measured as described below.

A film is prepared as described for the measurement of the discolorationratio after reduction cleaning of pigments.

The film is cut into 10 cm squares, and four squares are overlaid formeasuring the reflectance at 850 nm by the following method. Themeasuring instrument used is spectrophotograph U3400 produced byHitachi, Ltd. Furthermore, the reference white plate is a magnesiumoxide plate.

At first, the white plate is irradiated with light of 850 nm from thespectrophotograph, and the reflected light is condensed by anintegrating sphere. The intensity of the reflected light is measured,and the value is expressed as R100.

Then, similar measurement is performed for a sample to be measured, andthe obtained value is expressed as RSamp.

Using the R100 values and RSamp value obtained as described above, thevalue of the infrared reflectance of this invention is obtained from thefollowing formula.Infrared reflectance=(Rsamp)/(R100)×100

-   3. Method for measuring the chroma of a polyurethane film containing    pigments

The chroma of a polyurethane film containing pigments in this inventionrefers to the chroma of the polyurethane film produced using thepolyurethane solution to be impregnated into a fiber-entangled substratewhen the artificial leather of this invention is produced. Thecoagulated film produced as described for measuring the discolorationratio after reduction cleaning is cut into 10 cm squares, and foursquares are overlaid for measuring under the following conditions. Themeasured chroma is called the chroma of the polyurethane film.

As the measuring instrument, Minolta Spectrophotometer CM-3700d or afunctionally equivalent instrument is used. As the light source, ahalogen lamp is used, and D65 light source is used as the measuringlight source. The angle of visibility is 10 degrees, and magnesium oxideis used as the white plate for reference. The measuring diameter is 25.4mm, and SCE is used for treatment of regularly reflected light. Underthese conditions, the a* and b* in the L*a*b* color system specified byCIE (Commission Internationale de l'Eclairage) are obtained. The(a*²+b*²)^(1/2) obtained using the obtained values is the chroma of thepolyurethane film in this invention.

-   4. Method for measuring the infrared reflectance of an artificial    leather

The measuring method and definition are quite the same as in theabove-mentioned measurement of the infrared reflectance of pigments,except that an artificial leather is used instead of the coagulated filmof a polyurethane as the sample, and that the nap surface (the so-calledfront surface of a product) is used as the surface to be measured.

-   5. Method for measuring the light fastness of an artificial leather

An artificial leather is cut into a 7 cm square as a sample, and its napsurface (the so-called front surface of a product) is used as thesurface to be exposed to light. A polyurethane foam having the same size(7 cm square) as the sample, a thickness of about 10 mm and a specificgravity of about 0.02±0.005 is laminated on the back surface (thesurface not exposed to light) of the sample, and the laminate is set ina device for performing light irradiation under the followingconditions. After completion of light irradiation, the class is judgedusing the gray scale for color change specified in JIS L 0804.

As the light irradiator, a xenon weather meter {SC750-WAP (produced bySuga Test Instrument)} is used to perform light irradiation 38 cycles,with the following treatments (A) and (B) as one cycle.

(A) Irradiating at a radiance of 150 W/m², with a 73° C. black panel andat a relative humidity of 50% RH for 3.8 hours

(B) Irradiating at a radiance of 0 W/m² (without irradiation), at ablack panel temperature of 38° C. and at a relative humidity of 95% RHfor 1 hour

The class is judged in reference to a 9-stage criterion of class 1,class 2, class 3, class 4 and class 5, with intermediate classes addedbetween the respective classes as class 1-2, class 2-3, class 3-4 andclass 4-5 to the above-mentioned 5-stage criterion. For evaluation, atleast three points are taken from a larger-sized sample at random formeasurement, and the observed classes are averaged for judgment.

-   6. Method for measuring the surface temperature of an artificial    leather during light irradiation

An artificial leather cut into a 7 cm square is prepared, andthermolabels (Thermolabel 5E-100 and Thermolabel 5E-75, produced byNichiyu Giken Kogyo Co., Ltd.) were stuck to the nap surface (so-calledfront surface of a product), and an urethane foam having the same size(7 cm square) as that of the sample, a thickness of about 10 mm and aspecific gravity of about 0.02±0.005 is laminated on the back surface ofthe sample on the side opposite to the nap surface. It is set in adevice so that the thermolabel surfaces can be irradiated with light,and then irradiated with light. After completion of light irradiation,whether the colors of the thermolabels have changed is observed tomeasure the surface temperature.

For measuring the surface temperature, at least three points are takenfrom a larger-sized sample at random for measurement, and thetemperatures of the at least three samples are averaged.

The light irradiation is performed under the same conditions as used forthe above-mentioned measurement of light fastness.

That is, as the light irradiator, a xenon weather meter {SC750-WAP(produced by Suga Test Instrument)} is used to perform light irradiation38 cycles, with the following treatments (A) and (B) as one cycle.

(A) Irradiating at a radiance of 150 W/m², with a 73° C. black panel andat a relative humidity of 50% RH for 3.8 hours

(B) Irradiating at a radiance of 0 W/m² (without irradiation), at ablack panel temperature of 38° C. and at a relative humidity of 95% RHfor 1 hour

EXAMPLES

This invention is described below in reference to examples.

The light fastness and surface temperature of each artificial leatherproduct and the infrared reflectance and chroma, in this invention inthe respective examples and comparative examples were measured accordingto the methods described above. Specking was evaluated as describedbelow.

-   7. Evaluation of specking

In this invention, specking refers to a phenomenon in which theappearance on the surface of an artificial leather is degraded since thepolyurethane on the surface of the artificial leather becomes whitish tocause a color difference between the polyurethane and the fibers. Theoccurrence of specking was evaluated with eyes. A surface free fromspecking is indicated by o; a surface with some specking, Δ; and asurface with very conspicuous speckling, x.

Example 1

Staple fibers having polymers disposed in each other, with polyethyleneterephthalate as an island component, polystyrene as a sea component, anisland/sea ratio of 80/20 wt %, 25 islands per fiber and a conjugatefiber fineness of about 5 dtex were used and formed into a web using acard cross-lapper, which was then needle-punched to make a felt with aunit weight of 600 g/m². The felt was treated for being shrunken, anddried. Subsequently, the felt was impregnated with a polyvinyl alcoholaqueous solution, and dried.

The sheet was immersed in trichloroethylene, and mangled to remove thesea component, and the residue was dried.

On the other hand, an azo-based yellow pigment, and adiketopyrrolopyrrole-based red pigment, and a phthalocyanine-based bluepigment were dispersed and dissolved into dimethylformamide respectivelyby 0.2 wt %, 0.3 wt % and 0.25 wt % as solid contents based on the solidcontent of the following polyurethane, while a polycarbonate-basedpolyurethane was dispersed and dissolved by 12 wt % based on the weightof the entire solution, to obtain a polyurethane solution. The infraredreflectance of the coagulated film of the polyurethane solution was 88%.

The polyurethane solution was immersed into the island fibers by about29 parts as solid content per the island fibers, and solidified by a wetmethod, and the impregnated fibers were compressed and squeezed usingrolls so that dimethylformamide could be substantially perfectlyremoved. The sheet was washed with warm water and dried.

Then, the sheet was sliced into two sheets in the thickness direction,and one of the sheets was raised on one side using sand paper, to obtaina napped sheet.

The napped sheet was dyed beige using a disperse dye excellent in lightfastness, and treated for finishing.

The average single fiber fineness of the ultra-fine polyester fibersconstituting the suede-like artificial leather was about 0.2 dtex, andthe chroma obtained by solidifying the used polyurethane solution by awet method was 2.5.

The suede-like artificial leather was free from the occurrence ofspecking, being a suede-like artificial leather with a calm color tonegiving a high quality impression.

The infrared reflectance of the suede-like artificial leather at 850 nmwas measured and found to be 85%, and the surface temperature wasmeasured and found to be 75° C. Furthermore, the light fastness wasevaluated and found to show excellent performance of class 4. Moreover,the chroma of the pigments, the discoloration ratio after reductioncleaning of the pigments and the occurrence of specking wererespectively evaluated. The results are shown in Table 1.

Examples 2, 3 and 4, and Comparative Examples 1, 2, 3 and 4

Suede-like artificial leathers were obtained as described for Example 1,except that the pigments added to the polyurethane and theirconcentrations were as stated in Table 1, and that the hue of dyeing wasdark gray.

Evaluated were the light fastness of each artificial leather, thesurface temperature of each artificial leather, the occurrence ofspecking in each artificial leather, the infrared reflectance of eachartificial leather, the infrared reflectance of pigments, the chroma ofpigments, and the discoloration ratio after reduction cleaning ofpigments. The results are shown in Table 1.

The artificial leather obtained in Example 2 had excellent lightfastness of class 4, and was free from the occurrence of specking,excellent in surface appearance, and dark gray.

The artificial leather obtained in Example 3 had excellent lightfastness of class 3-4, was free from the occurrence of specking, and hada calm hue deeper than that of Example 2.

The artificial leather obtained in Example 4 had excellent lightfastness of class 3-4, was free from the occurrence of specking, and hada deep and calm hue, though the added amounts of pigments were smallerthan those of Examples 2 and 3.

Comparative Example 1 was free from specking and excellent in surfaceappearance, but had poor light fastness of class 2.

The artificial leather of Comparative Example 2 was had somewhat poorlight fastness of class 2-3, was not deep in hue, had specking to someextent, and was poor in surface appearance, hence poor in high classimpression.

The artificial leather of Comparative Example 3 had excellent lightfastness of class 4, but had much specking, and was not deep in hue,being very poor in surface appearance.

The artificial leather of Comparative Example 4 had no effect ofpolyurethane coloration though the amount of the pigment added to thepolyurethane was large, had much specking, and was not deep in hue,being very poor in surface appearance. TABLE 1 Property values ofpigments Property values of artificial leather Discoloration InfraredLight Surface Infrared ratio after Concentrations reflectance fastnesstemperature reflectance Chroma reduction Pigments added of pigments (%)(%) (class) (° C.) Specking (%) C* cleaning (%) Example 1 Yellow (azotype) 0.2 85 4 75 ∘ 88 2.5 2.0 Red (DPP type) 0.3 Blue (phthalocyanine0.25 type) Example 2 Yellow (azo type) 2.3 80 4 80 ∘ 83 1.8 1.6 Red (DPPtype) 1.5 Blue (phthalocyanine 1.4 type) Example 3 Yellow (azo type) 1.979 3-4 83 ∘ 82 1.3 2.7 Red (DPP type) 0.8 Red (anthraquinone 0.9 type)Blue (phthalocyanine 2.1 type) Example 4 Yellow (azo type) 0.8 81 3-4 86∘ 78 2.1 1.3 Yellow (imidazolone 0.7 type) Red (DPP type) 0.7 Red(anthraquinone 0.8 type) Blue (phthalocyanine 2.0 type) ComparativeCarbon black 2.0 37 2 115 ∘ 15 0.9 0.3 Example 1 Comparative Carbonblack 0.06 51 2-3 110 Δ 32 1.5 0.2 Example 2 Comparative No pigmentadded 0.0 88 4 75 x 89 1.6 0.0 Example 3 Comparative Black pigment 12.673 2-3 95 x 75 2.8 63 Example 4 (perylene type)DPP: Abbreviation of diketopyrrolopyrroleNote:C*: (a*² + b*²)^(1/2)Industrial Applicability

The suede-like artificial leather obtained by this invention is asuede-like artificial leather having, especially, high qualityappearance, surface touch, brilliant coloration and good surfaceappearance. It is also very excellent in the light fastness of itscoloration. Because of these properties, the artificial leather can befavorably used not only in high quality clothing field, but also invarious other fields including the interior materials of automobilessuch as, especially, car seats, and furniture use.

This invention can provide a suede-like artificial leather highlyimproved in light fastness, which can provide more available huevariations, especially, for the interior materials of automobiles suchas car seats, to expand the market and to encourage new demands, eventhough the conventional deep colored or medium deep colored artificialleathers could not be used because of such problems as fading andcrocking.

1. A suede-like artificial leather, which comprising a fiber-entangledsubstrate mainly containing ultra-fine polyester fibers with a fiberfineness of 0.7 dtex or less and a polyurethane, and is dyed, whereinsaid polyurethane contains at least one each of yellow pigments, redpigments and blue pigments, and said artificial leather satisfies all ofthe following properties (1) through (3) as measured by the methodsdescribed in the specification; (1) The infrared reflectance at 850 nmis 60% or more; (2) The surface temperature during light irradiation is105° C. or lower; (3) The light fastness is class 3 or better.
 2. Asuede-like artificial leather, according to claim 1, wherein thepolyurethane is mainly a polycarbonate-based polyurethane.
 3. A methodfor producing a suede-like artificial leather excellent in lightfastness, in which a fiber-entangled substrate mainly containingultra-fine polyester fibers with a fiber fineness of 0.7 dtex or less isimpregnated with a polyurethane, wherein the polyurethane solution usedcontains at least one each of yellow pigments, red pigments and bluepigments in such a manner that the coagulated film of the polyurethanesolution satisfies all the following properties (4) through (6) when itis evaluated according to the methods described in the specification;(4) The infrared reflectance at 850 nm is 60% or more; (5) Thediscoloration ratio after reduction cleaning is 20% or less; (6) Thechroma is 10 or less.
 4. A method for producing a suede-like artificialleather, according to claim 3, wherein a polycarbonate-basedpolyurethane is mainly used as the polyurethane.